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1.
Clin Genet ; 105(3): 313-316, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-37990933

RESUMO

We report the case of a 12-year-old girl and her father who both had marked postnatal tall stature, camptodactyly and clinodactyly, scoliosis and juvenile-onset hearing loss. The CATSHL (CAmptodactyly - Tall stature - Scoliosis - Hearing Loss syndrome) syndrome was suspected, and molecular analysis revealed a hitherto unreported, monoallelic variant c.1861C>T (p.Arg621Cys) in FGFR3. This variant affects the same residue, but is different than, the variant p.Arg621His reported in the two families with dominant CATSHL described so far. Interestingly, peg-shaped incisors were observed in the proband, a feature never reported in CATSHL but typical of another FGFR3-related condition, LADD (Lacrimo - Auricolo - Dento - Digital) syndrome. The FGFR3 p.Arg621Cys variant seems to be a newly identified cause of CATSHL syndrome with some phenotypic overlap with the LADD syndrome.


Assuntos
Anormalidades Múltiplas , Doenças do Desenvolvimento Ósseo , Surdez , Deformidades Congênitas da Mão , Perda Auditiva , Doenças do Aparelho Lacrimal , Deformidades Congênitas dos Membros , Escoliose , Sindactilia , Anormalidades Dentárias , Feminino , Humanos , Criança , Escoliose/genética , Perda Auditiva/genética , Síndrome
2.
Acta Biomed ; 94(S3): e2023157, 2023 08 30.
Artigo em Inglês | MEDLINE | ID: mdl-37695189

RESUMO

BACKGROUND AND AIM: Proper nutrition during childhood and puberty is essential to ensure healthy growth of children and good health in adulthood. Different types of interventions have been suggested to promote nutritional health in children. This systematic review aims to summarize the available evidence from experimental studies on the efficacy of digital media tools for the promotion of a healthy diet in school-aged children. METHODS: According to PRISMA guidelines, a literature search was conducted in the three main electronic databases (PubMed/Medline, Embase e Scopus) until April 2022. We included all experimental studies assessing the effectiveness of digital media tools for nutritional health promotion in children from 5 to 12 years of age. RESULTS: Four studies were included in our analysis, all carried out in school settings. Three of them investigated the use of a videogame, while one study involved watching a cartoon. Each intervention tested was effective in promoting a healthy diet in school-aged children in the short term, regardless of the type of intervention and age of the children involved. A statistically significant increase was observed post-intervention in all studies, both in knowledge of food groups and food frequencies, and in practices (i.e. the amount of fruit and vegetables servings consumed per meal), although the effect faded over time (when follow-up was available). CONCLUSIONS: Digital media tools can be used to effectively implement health promotion interventions to improve knowledge and adherence to healthy diets in school-aged children. Further studies are needed to assess the long-term effectiveness of these interventions.


Assuntos
Dieta Saudável , Internet , Humanos , Criança , Bases de Dados Factuais , Alimentos , Promoção da Saúde
3.
Vaccines (Basel) ; 10(11)2022 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-36366331

RESUMO

An infodemic represents a concern for public health, influencing the general population's perceptions of key health issues. Misinformation is rapidly spread by social media, particularly among young generations. We used data from the WHO "Social Media and COVID-19" study, which was conducted in 24 countries worldwide on over 23,000 subjects aged 18-40 years, to explore Generation Z and Millennials' models for health-information-seeking behaviors on social media. We summarized data on the most used sources of information, content of interest, and content sharing, as well as the sentiment toward the infodemic, through descriptive statistics and Chi-square test to verify the differences between groups. Among the survey respondents, 9475 (40.3%) were from high-income countries (HIC), 8000 (34.1%) from upper-middle-income countries (UMIC), and 6007 (25.6%) from lower-middle-income countries (LMIC). Social media were the most used sources of information to retrieve news on COVID-19 disease (about 79% in HIC, 87% in UMIC, and 90% in LIC) and the COVID-19 vaccine (about 78% in HIC and about 88% in UMIC and LIC). More than a half of the young respondents declared that they pay attention to scientific contents (about 51% in HIC, 59% in UMIC, and 55% in LMIC). Finally, most young participants reported feeling overwhelmed by the infodemic. However, this sentiment did not stop them from seeking information about COVID-19. Our findings highlight the importance of shaping public health interventions and campaigns on social media platforms and leveraging scientific contents. Public health authorities should work also on strategies to improve the digital literacy of the population as a driving force to empower them and achieve better health outcomes.

4.
Prev Med ; 164: 107264, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-36150446

RESUMO

Worldwide, the COVID-19 pandemic disrupted healthcare services, including cervical cancer management, and an increased burden for this condition is expected. This systematic review synthetizes the available evidence on the impact of the pandemic on prevention, diagnosis and treatment of cervical cancer. Searches were performed on PubMed, Embase, and Scopus for relevant studies on these topics with the purpose of comparing service access and care delivery before and during COVID-19 pandemic. Due to the methodological heterogeneity among the studies, findings were narratively discussed. Of the 715 screened titles and abstracts, 33 articles were included, corresponding to 42 reports that covered the outcomes of interest: vaccination against human papillomavirus (HPV) (6 reports), cancer screening (19), diagnosis (8), and treatment (8). Seven studies observed reductions in HPV vaccination uptake and coverage during COVID-19. Reports on cervical screening and cancer diagnosis activities showed a substantial impact of the pandemic on access to screening services and diagnostic procedures. All but one study that investigated cervical cancer treatment reported changes in the number of women with cervical lesions who received treatments, as well as treatment delay and interruption. With a major impact during the first wave in 2020, COVID-19 and restriction measures resulted in a substantial disruption in cervical cancer prevention and management, with declines in screening and delays in treatment. Taken together, findings from this systematic review calls for urgent policy interventions for recovering cervical cancer prevention and care.


Assuntos
COVID-19 , Infecções por Papillomavirus , Vacinas contra Papillomavirus , Neoplasias do Colo do Útero , Feminino , Humanos , Neoplasias do Colo do Útero/diagnóstico , Neoplasias do Colo do Útero/prevenção & controle , Infecções por Papillomavirus/diagnóstico , Infecções por Papillomavirus/prevenção & controle , Infecções por Papillomavirus/epidemiologia , COVID-19/diagnóstico , COVID-19/prevenção & controle , Detecção Precoce de Câncer/métodos , Pandemias/prevenção & controle , Assistência ao Paciente
5.
Sci Rep ; 11(1): 12635, 2021 06 16.
Artigo em Inglês | MEDLINE | ID: mdl-34135378

RESUMO

The study of ancient DNA is revolutionizing our understanding of paleo-ecology and the evolutionary history of species. Insects are essential components in many ecosystems and constitute the most diverse group of animals. Yet they are largely neglected in ancient DNA studies. We report the results of the first targeted investigation of insect ancient DNA to positively identify subfossil insects to species, which includes the recovery of endogenous content from samples as old as ~ 34,355 ybp. Potential inhibitors currently limiting widespread research on insect ancient DNA are discussed, including the lack of closely related genomic reference sequences (decreased mapping efficiency) and the need for more extensive collaborations with insect taxonomists. The advantages of insect-based studies are also highlighted, especially in the context of understanding past climate change. In this regard, insect remains from ancient packrat middens are a rich and largely uninvestigated resource for exploring paleo-ecology and species dynamics over time.


Assuntos
Artrópodes/genética , DNA Antigo/análise , Análise de Sequência de DNA/veterinária , Sigmodontinae/parasitologia , Animais , DNA Mitocondrial/genética , Fósseis , Biblioteca Gênica , Sequenciamento de Nucleotídeos em Larga Escala , RNA Ribossômico 28S/genética , Sigmodontinae/genética
6.
Curr Biol ; 31(8): 1771-1779.e7, 2021 04 26.
Artigo em Inglês | MEDLINE | ID: mdl-33592193

RESUMO

Palaeogenomes provide the potential to study evolutionary processes in real time, but this potential is limited by our ability to recover genetic data over extended timescales.1 As a consequence, most studies so far have focused on samples of Late Pleistocene or Holocene age, which covers only a small part of the history of many clades and species. Here, we report the recovery of a low coverage palaeogenome from the petrous bone of a ∼360,000 year old cave bear from Kudaro 1 cave in the Caucasus Mountains. Analysis of this genome alongside those of several Late Pleistocene cave bears reveals widespread mito-nuclear discordance in this group. Using the time interval between Middle and Late Pleistocene cave bear genomes, we directly estimate ursid nuclear and mitochondrial substitution rates to calibrate their respective phylogenies. This reveals post-divergence mitochondrial transfer as the dominant factor explaining their mito-nuclear discordance. Interestingly, these transfer events were not accompanied by large-scale nuclear introgression. However, we do detect additional instances of nuclear admixture among other cave bear lineages, and between cave bears and brown bears, which are not associated with mitochondrial exchange. Genomic data obtained from the Middle Pleistocene cave bear petrous bone has thus facilitated a revised evolutionary history of this extinct megafaunal group. Moreover, it suggests that petrous bones may provide a means of extending both the magnitude and time depth of palaeogenome retrieval over substantial portions of the evolutionary histories of many mammalian clades.


Assuntos
Ursidae , Animais , DNA Mitocondrial , Fósseis , Genoma , Genômica , Filogenia , Ursidae/genética
7.
BMC Genomics ; 21(1): 854, 2020 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-33267779

RESUMO

BACKGROUND: Numerous megafauna species from northern latitudes went extinct during the Pleistocene/Holocene transition as a result of climate-induced habitat changes. However, several ungulate species managed to successfully track their habitats during this period to eventually flourish and recolonise the holarctic regions. So far, the genomic impacts of these climate fluctuations on ungulates from high latitudes have been little explored. Here, we assemble a de-novo genome for the European moose (Alces alces) and analyse it together with re-sequenced nuclear genomes and ancient and modern mitogenomes from across the moose range in Eurasia and North America. RESULTS: We found that moose demographic history was greatly influenced by glacial cycles, with demographic responses to the Pleistocene/Holocene transition similar to other temperate ungulates. Our results further support that modern moose lineages trace their origin back to populations that inhabited distinct glacial refugia during the Last Glacial Maximum (LGM). Finally, we found that present day moose in Europe and North America show low to moderate inbreeding levels resulting from post-glacial bottlenecks and founder effects, but no evidence for recent inbreeding resulting from human-induced population declines. CONCLUSIONS: Taken together, our results highlight the dynamic recent evolutionary history of the moose and provide an important resource for further genomic studies.


Assuntos
Cervos , Variação Genética , Animais , DNA Mitocondrial/genética , Cervos/genética , Demografia , Europa (Continente) , América do Norte , Filogenia , Análise de Sequência de DNA
8.
Sci Rep ; 10(1): 12621, 2020 07 28.
Artigo em Inglês | MEDLINE | ID: mdl-32724178

RESUMO

The cave lion is an extinct felid that was widespread across the Holarctic throughout the Late Pleistocene. Its closest extant relative is the lion (Panthera leo), but the timing of the divergence between these two taxa, as well as their taxonomic ranking are contentious. In this study we analyse 31 mitochondrial genome sequences from cave lion individuals that, through a combination of 14C and genetic tip dating, are estimated to be from dates extending well into the mid-Pleistocene. We identified two deeply diverged and well-supported reciprocally monophyletic mitogenome clades in the cave lion, and an additional third distinct lineage represented by a single individual. One of these clades was restricted to Beringia while the other was prevalent across western Eurasia. These observed clade distributions are in line with previous observations that Beringian and European cave lions were morphologically distinct. The divergence dates for these lineages are estimated to be far older than those between extant lions subspecies. By combining our radiocarbon tip-dates with a split time prior that takes into account the most up-to-date fossil stem calibrations, we estimated the mitochondrial DNA divergence between cave lions and lions to be 1.85 Million ya (95% 0.52- 2.91 Mya). Taken together, these results support previous hypotheses that cave lions existed as at least two subspecies during the Pleistocene, and that lions and cave lions were distinct species.


Assuntos
Biodiversidade , Cavernas , Leões/genética , Animais , Genoma Mitocondrial , Geografia , Filogenia , Especificidade da Espécie , Manejo de Espécimes , Fatores de Tempo
9.
Curr Biol ; 29(10): 1695-1700.e6, 2019 05 20.
Artigo em Inglês | MEDLINE | ID: mdl-31080081

RESUMO

Historically, the giant panda was widely distributed from northern China to southwestern Asia [1]. As a result of range contraction and fragmentation, extant individuals are currently restricted to fragmented mountain ranges on the eastern margin of the Qinghai-Tibet plateau, where they are distributed among three major population clusters [2]. However, little is known about the genetic consequences of this dramatic range contraction. For example, were regions where giant pandas previously existed occupied by ancestors of present-day populations, or were these regions occupied by genetically distinct populations that are now extinct? If so, is there any contribution of these extinct populations to the genomes of giant pandas living today? To investigate these questions, we sequenced the nuclear genome of an ∼5,000-year-old giant panda from Jiangdongshan, Tengchong County in Yunnan Province, China. We find that this individual represents a genetically distinct population that diverged prior to the diversification of modern giant panda populations. We find evidence of differential admixture with this ancient population among modern individuals originating from different populations as well as within the same population. We also find evidence for directional gene flow, which transferred alleles from the ancient population into the modern giant panda lineages. A variable proportion of the genomes of extant individuals is therefore likely derived from the ancient population represented by our sequenced individual. Although extant giant panda populations retain reasonable genetic diversity, our results suggest that this represents only part of the genetic diversity this species harbored prior to its recent range contractions.


Assuntos
DNA Antigo/análise , Variação Genética , Genoma , Ursidae/genética , Animais , China , Espécies em Perigo de Extinção , Masculino
10.
PLoS One ; 14(5): e0216883, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31095634

RESUMO

The extant diversity of horses (family Equidae) represents a small fraction of that occurring over their evolutionary history. One such lost lineage is the subgenus Sussemionus, which is thought to have become extinct during the Middle Pleistocene. However, recent molecular studies and morphological analysis have revealed that one of their representatives, E. ovodovi, did exist in Siberia during the Late Pleistocene. Fossil materials of E. ovodovi have thus far only been found in Russia. In this study, we extracted DNA from three equid fossil specimens excavated from northeastern China dated at 12,770-12,596, 29,525-28,887 and 40,201-38,848 cal. yBP, respectively, and retrieved three near-complete mitochondrial genomes from the specimens. Phylogenetic analyses cluster the Chinese haplotypes together with previously published Russian E. ovodovi, strongly supporting the assignment of these samples to this taxon. The molecular identification of E. ovodovi in northeastern China extends the known geographical range of this fossil species by several thousand kilometers to the east. The estimated coalescence time of all E. ovodovi haplotypes is approximately 199 Kya, with the Chinese haplotypes coalescing approximately 130 Kya. With a radiocarbon age of 12,770-12,596 cal. yBP, the youngest sample in this study represents the first E. ovodovi sample dating to the terminal Pleistocene, moving the extinction date of this species forwards considerably compared to previously documented fossils. Overall, comparison of our three mitochondrial genomes with the two published ones suggests a genetic diversity similar to several extant species of the genus Equus.


Assuntos
Evolução Biológica , DNA Antigo , Equidae , Genoma Mitocondrial , Haplótipos , Filogenia , Animais , Equidae/classificação , Equidae/genética
11.
Mol Ecol Resour ; 18(6): 1196-1208, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-29877032

RESUMO

The prevalence of contaminant microbial DNA in ancient bone samples represents the principal limiting factor for palaeogenomic studies, as it may comprise more than 99% of DNA molecules obtained. Efforts to exclude or reduce this contaminant fraction have been numerous but also variable in their success. Here, we present a simple but highly effective method to increase the relative proportion of endogenous molecules obtained from ancient bones. Using computed tomography (CT) scanning, we identify the densest region of a bone as optimal for sampling. This approach accurately identifies the densest internal regions of petrous bones, which are known to be a source of high-purity ancient DNA. For ancient long bones, CT scans reveal a high-density outermost layer, which has been routinely removed and discarded prior to DNA extraction. For almost all long bones investigated, we find that targeted sampling of this outermost layer provides an increase in endogenous DNA content over that obtained from softer, trabecular bone. This targeted sampling can produce as much as 50-fold increase in the proportion of endogenous DNA, providing a directly proportional reduction in sequencing costs for shotgun sequencing experiments. The observed increases in endogenous DNA proportion are not associated with any reduction in absolute endogenous molecule recovery. Although sampling the outermost layer can result in higher levels of human contamination, some bones were found to have more contamination associated with the internal bone structures. Our method is highly consistent, reproducible and applicable across a wide range of bone types, ages and species. We predict that this discovery will greatly extend the potential to study ancient populations and species in the genomics era.


Assuntos
Osso e Ossos/química , DNA Antigo/análise , DNA Antigo/isolamento & purificação , Fósseis , Tomografia Computadorizada por Raios X/métodos , Humanos
12.
Proc Biol Sci ; 284(1867)2017 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-29167359

RESUMO

It is unclear whether Indo-European languages in Europe spread from the Pontic steppes in the late Neolithic, or from Anatolia in the Early Neolithic. Under the former hypothesis, people of the Globular Amphorae culture (GAC) would be descended from Eastern ancestors, likely representing the Yamnaya culture. However, nuclear (six individuals typed for 597 573 SNPs) and mitochondrial (11 complete sequences) DNA from the GAC appear closer to those of earlier Neolithic groups than to the DNA of all other populations related to the Pontic steppe migration. Explicit comparisons of alternative demographic models via approximate Bayesian computation confirmed this pattern. These results are not in contrast to Late Neolithic gene flow from the Pontic steppes into Central Europe. However, they add nuance to this model, showing that the eastern affinities of the GAC in the archaeological record reflect cultural influences from other groups from the East, rather than the movement of people.


Assuntos
Variação Genética , Genoma Humano , Migração Humana/história , Idioma/história , Arqueologia , Teorema de Bayes , Núcleo Celular/genética , DNA Antigo/análise , DNA Mitocondrial/genética , Europa (Continente) , História Antiga , Humanos
13.
Nat Genet ; 33(1): 21-2, 2003 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-12469120

RESUMO

Animal models indicate that the antimicrobial peptide hepcidin (HAMP; OMIM 606464) is probably a key regulator of iron absorption in mammals. Here we report the identification of two mutations (93delG and 166C-->T) in HAMP on 19q13 in two families with a new type of juvenile hemochromatosis.


Assuntos
Peptídeos Catiônicos Antimicrobianos/genética , Hemocromatose/genética , Mutação/genética , Sequência de Aminoácidos , Peptídeos Catiônicos Antimicrobianos/química , Sequência de Bases , Criança , Análise Mutacional de DNA , Feminino , Hepcidinas , Humanos , Masculino , Dados de Sequência Molecular , Linhagem , Polimorfismo Conformacional de Fita Simples
14.
Blood ; 100(10): 3782-9, 2002 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-12393650

RESUMO

Human transferrin receptor-2 (TFR-2) is a protein highly homologous to TFR-1/CD71 and is endowed with the ability to bind transferrin (TF) with low affinity. High levels of TFR-2 mRNA were found in the liver and in erythroid precursors. Mutations affecting the TFR-2 gene led to hemochromatosis type 3, a form of inherited iron overload. Several issues on distribution and function of the receptor were answered by raising a panel of 9 monoclonal antibodies specific for TFR-2 by immunizing mice with murine fibroblasts transfected with the human TFR-2 cDNA. A polyclonal antiserum was also produced in mice immunized with 3 peptides derived from the TFR-2 sequence, exploiting an innovative technique. The specificity of all the reagents produced was confirmed by reactivity with TFR-2(+) target cells and simultaneous negativity with TFR-1(+) cells. Western blot analyses showed a dominant chain of approximately 90 kDa in TFR-2 transfectants and HepG2 cell line. Analysis of distribution in normal tissues and in representative cell lines revealed that TFR-2 displays a restricted expression pattern--it is present at high levels in hepatocytes and in the epithelial cells of the small intestine, including the duodenal crypts. Exposure of human TFR-2(+) cells to TF-bound iron is followed by a significant up-regulation and relocalization of membrane TFR-2. The tissue distribution pattern, the behavior following exposure to iron-loaded TF, and the features of the disease resulting from TFR-2 inactivation support the hypothesis that TFR-2 contributes to body iron sensing.


Assuntos
Anticorpos Monoclonais , Receptores da Transferrina/imunologia , Receptores da Transferrina/metabolismo , Animais , Anticorpos Monoclonais/biossíntese , Anticorpos Monoclonais/imunologia , Especificidade de Anticorpos , Endotélio/química , Hepatócitos/química , Humanos , Soros Imunes/imunologia , Imuno-Histoquímica , Intestinos/citologia , Camundongos , Camundongos Endogâmicos BALB C , Distribuição Tecidual , Transferrina/farmacologia , Células Tumorais Cultivadas , Regulação para Cima/efeitos dos fármacos
15.
Br J Haematol ; 117(4): 973-9, 2002 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-12060140

RESUMO

Juvenile haemochromatosis or haemochromatosis type 2 is a rare autosomal recessive disorder which causes iron overload at a young age, affects both sexes equally and is characterized by a prevalence of hypogonadism and cardiopathy. Patients with haemochromatosis type 2 have been reported in different ethnic groups. Linkage to chromosome 1q has been established recently, but the gene remains unknown. We report the analysis of the phenotype of 29 patients from 20 families of different ethnic origin with a juvenile 1q-associated disease. We also compared the clinical expression of 26 juvenile haemochromatosis patients with that of 93 C282Y homozygous males and of 11 subjects with haemochromatosis type 3. Patients with haemochromatosis type 2 were statistically younger at presentation and had a more severe iron burden than C282Y homozygotes and haemochromatosis type 3 patients. They were more frequently affected by cardiopathy, hypogonadism and reduced glucose tolerance. In contrast cirrhosis was not statistically different among the three groups. These data suggest that the rapid iron accumulation in haemochromatosis type 2 causes preferential tissue damage. Our results clarify the natural history of the disease and are compatible with the hypothesis that the HFE2 gene has greater influence on iron absorption than other haemochromatosis-associated genes.


Assuntos
Hemocromatose/genética , Adolescente , Adulto , Idoso , Criança , Pré-Escolar , Mapeamento Cromossômico , Cromossomos Humanos Par 1 , Feminino , Ferritinas/sangue , Genótipo , Hemocromatose/metabolismo , Humanos , Ferro/metabolismo , Sobrecarga de Ferro/genética , Fígado/metabolismo , Masculino , Pessoa de Meia-Idade , Mutação , Fenótipo , Transferrina/análise
16.
Gastroenterology ; 122(5): 1295-302, 2002 May.
Artigo em Inglês | MEDLINE | ID: mdl-11984516

RESUMO

BACKGROUND & AIMS: Although most patients with hereditary hemochromatosis are homozygous for a single mutation of the HFE gene on chromosome 6p, accumulating evidence indicates that the disease is genetically heterogeneous. Type 3 hemochromatosis, recently described in 4 families, is linked to mutations of the gene encoding transferrin receptor 2 on chromosome 7q22. Here we report data from a family carrying a new mutation of the transferrin receptor 2 gene. METHODS: Detailed clinical and histopathologic documentation was available for most family members. The entire coding sequence and exon/intron boundaries of the transferrin receptor 2 gene were analyzed by direct sequencing. RESULTS: A 12-nucleotide deletion in exon 16, causing the loss of 4 amino acids (AVAQ 594-597 del), was detected at the homozygous state in the 3 patients with histologically proven iron overload. The deletion segregated with the disease within the family and was not found in 100 healthy controls. Some clinical and pathologic characteristics, such as low penetrance in the premenopausal woman, and early iron deposition in periportal hepatocytes resembled those of classic, HFE-related hemochromatosis. CONCLUSIONS: Our data support the role of the transferrin receptor 2 gene in hemochromatosis type 3 as well as its critical involvement in the maintenance of iron homeostasis in humans.


Assuntos
Hemocromatose/genética , Mutação , Receptores da Transferrina/genética , Adolescente , Adulto , Feminino , Hemocromatose/patologia , Humanos , Masculino , Pessoa de Meia-Idade
17.
Blood Cells Mol Dis ; 29(3): 465-70, 2002.
Artigo em Inglês | MEDLINE | ID: mdl-12547237

RESUMO

A rare recessive disorder which leads to iron overload and severe clinical complications similar to those reported in HFE-related hemochromatosis has been delineated and sometimes called hemochromatosis type 3. The gene responsible is Transferrin Receptor 2 (TFR2), which maps to chromosome 7q22. The TFR2 gene presents a significative homology to transferrin receptor (TFRC) gene, encodes for a transmembrane protein with a large extracellular domain, is able to bind transferrin, even if with lower affinity than TFRC. The TFR2 function is still unclear. The transcript does not contain IRE elements and is not modified by the cellular iron status. At variance with TFRC, interactions between TFR2 and HFE do not occur, at least in their soluble forms. TFR2 is spliced in two alternative forms, alfa and beta. The alfa form is strongly expressed in the liver. The beta form, codified from a start site in exon 4 of the alpha, has a low and ubiquitous expression. Using anti-TFR2 monoclonal antibodies we have confirmed expression of the protein in the liver but also in duodenal epithelial cells, and studied the protein functional behaviour in cell lines, in response to iron addition, iron deprivation and olo-transferrin exposure. Our results suggest a regulatory role of TFR2 in iron metabolism. Five TFR2 homozygous mutations have been documented in HFE3 patients: a nonsense mutation (Y250X); a C insertion that causes a frameshift and a premature stop codon (E60X); a missense mutation (M172K); a 12 basepair deletion in exon 16, that causes 4 aminoacid loss (AVAQ 594-597del) in the extracellular domain of TFR2; a missense mutation in exon 17 (Q690P). The mutation analysis supports the hypothesis that all are private mutations. The pathogenetic role of TFR2 in hemochromatosis has been recently further demonstrated through the targeted expression of the Y250X human mutation in mice, which develop sings of iron overload identical to the human disease. Although the rarity of TFR2 mutations limits their usefulness in diagnostic/screening programs, their study can contribute to a better understanding of the protein function.


Assuntos
Hemocromatose/genética , Mutação , Receptores da Transferrina/genética , Hemocromatose/etiologia , Humanos , Células K562 , Receptores da Transferrina/deficiência , Receptores da Transferrina/metabolismo
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